There was no Look Back team at Facebook — when the company decided to make videos celebrating the past posts of each member, it pulled people from across different groups to complete the task. Originally they thought the process would take months, but as Alexey Spiridonov writes on Facebook's engineering blog, they did it in just a few weeks — and with time to spare. There were many obstacles to consider, including how the Look Back videos would affect Facebook's internal infrastructure, but also how they would debut the videos on time as the launch of the company's new Paper app rapidly approached. Read the entire blog post to see how they pulled it off, and how they managed to exceed their own expectations by rendering over 9 million videos per hour at Look Back's peak.